1. Field of the Invention
The present invention relates generally to the field of completion systems for oil and gas production wells. More particularly, the invention relates to a technique for completing a production well through the use of a submersible pumping system to which power is routed through the equipment in a novel manner.
2. Description of the Related Art
A wide variety of systems are known and have been proposed for producing fluids of economic interest from subterranean geological formations. In formations providing sufficient pressure to force the fluids to the earth's surface, the fluids may be collected and processed without the use of artificial pumping systems. Where, however, well pressures are insufficient to raise fluids to the collection point, artificial means are typically employed, such as submersible pumping systems.
The particular configurations of submersible pumping systems may vary widely depending upon the well conditions, the geological formations present, and the desired completion approach. In general however, such systems typically include an electric motor driven by power supplied from the earth's surface. The motor is coupled to a pump which draws wellbore fluids from a production horizon and imparts sufficient head to force the fluids to the collection point. Such systems may include additional components especially adapted for the particular wellbore fluids or mix of fluids, including gas/oil separators, oil/water separators, water injection pumps, and so forth.
Submersible pumping systems may be deployed in a number of different manners. Conventionally, such systems were deployed at the end of a high tensile strength cable assembly. Power conductors, bundled in a separate assembly or in a common assembly with the suspension cables, served to supply power to the submersible electric motor. Other, more recent, deployment schemes include arrangements in which the submersible pumping system is suspended from a conduit, such as a length of coiled tubing. In systems of this type, the power cable may be enclosed in the conduit, or may be external to the conduit, typically in an annular region between the wellbore casing and the conduit. The latter arrangement is often preferred due to the need to convey the production fluids, typically petroleum and entrained minerals, through the conduit to the earth's surface.
While both cable and coiled tubing deployed pumping systems of the type described above are generally adequate for many applications, they are not without drawbacks. For example, where a conduit is used to deploy the system, the annular region surrounding the conduit often provides a greater cross-sectional area for the flow of production fluids. However, in certain completions, more than one production fluid is displaced, such as petroleum in one conduit and natural gas in another conduit or in the annular area. Recently, systems have been proposed for transmitting gas in a conduit, such as coiled tubing, and oil in the larger annular area between the conduit and the wellbore casing. These systems are particularly attractive where environmental conditions permit direct contact between the production fluids and the wellbore casing, or where liners or other protective coatings may be employed within the casing. However, such systems often call for the placement of a pumping system below a packer used to separate the pump inlet zone of the well from the pump outlet or discharge zone. A difficulty in these systems arises in conveying electrical power through the packer to the lower zone in which the submersible electric motor is positioned.
There is a need, therefore, for an improved technique for conveying power and control signals to equipment below a packer in a well completion. There is a particular need for a completion which provides easily field-installable electrical connections which can be made in a sealed manner during initial installation of pumping systems and similar equipment.